An uninterruptible power supply (UPS) is an apparatus that provides a supply of back-up power in the event of a loss of utility, for the purposes of protecting the load supported by the utility. The load may include an individual computer, a server in a datacenter, or another load depending on application. The supply of back-up power is at least enough to start a standby power source, such as a generator or an alternate utility line, or to properly shut down the load. This supply of back-up power is stored by the UPS in batteries, supercapacitors, or flywheels.